1. Field of the Invention
The present invention refers to a device for producing by means of laser energy a plurality of connections between contact elements of respective contact element pairs, said contact element pairs being arranged essentially in one plane and the contact element surfaces to be connected extending essentially parallel to this plane.
The present invention is, for example, used for producing bonds in the field of SMD technology (SMD=surface mounted device). In addition, the present invention is adapted to be used in the TAB technology (TAB tape automatic bonding=automatic film bonding) for bonding inner and outer connecting leads, the so-called inner-lead and outer-lead bonding.
Furthermore, the present invention can also be used for connecting fine wires or little tapes or the like.
2. Description of Prior Art
U.S. Pat. No. 4,845,335 describes a device for electrically connecting contact elements in the case of which contacts located on a TAB tape are connected to the contacts of an integrated circuit. In so doing, the contacts on the tape are brought into superpostion with the contacts on the integrated circuit, whereupon said contacts are interconnected by means of laser radiation. In order to achieve a good reproducability of the connections, the distance between the contacts to be connected must be minimized. According to a general rule, the distance must not be larger than approx. 10% of the thickness of the contact elements. With an increasing degree of miniaturization, the connections become smaller and smaller, whereby the dimensions of the contact geometries decrease so that it becomes problematic to fulfil these requirements.
In U.S. Pat. No. 4,845,335 a gas stream is used for applying pressure to the contact elements, said gas stream being directed onto the contact elements by means of a nozzle and the laser beam used for connection and the gas stream produced by said nozzle being coaxial.
The known device is, however, not optimal for connecting contact elements by means of laser energy, since the laser energy available is not optimally converted into thermal engery for connecting the contacts.
DE-A-3941558 discloses a laser connecting device which is suitable for spot welding, brazing or soldering. In this known device, the laser energy is conducted to the connection point by means of an optical fibre. In so doing, the optical fibre is held in a tool, which serves as a holder, in spaced relationship with the connection point, a pressure being applied to the connection point, i.e. the contact elements to be connected, via said tool.
DE-A-1958430 describes a device for connecting contact elements by means of a laser welding process, said device making use of a quartz mandrel for transmitting the laser energy to the connection point. The quartz mandrel also serves to apply a pressure to the connection point.